Multiconductor type broad band antenna



Aug 23 1966 TAucHlRo NoGucl-u ETAL 3268,59@

MULTIcoNDucToR TYPE BROAD BAND ANTENNA Filed April s, 1964 United States Patent O 3,268,904 MULTICONDUCTOR TYPE BROAD BAND ANTENNA Taiichiro Noguchi and Kunihiko Iki, Tokyo, and Rsaburo Sato, Sendai-shi, Japan, assignors to Yagi Antenna Co.,

Ltd., Kanda, Chiyodaku, Tokyo, Japan, a corporation of Japan Filed Apr. 3, 1964, Ser. No. 357,036 1 Claim. (Cl. 343-794) This invention relates to a multiconductor type broad band antenna which can effectively operate over an eX- tremely broad frequency band.

When a plurality of parallel conductors are suitably combined a current component serving as radiation and a current component acting as a reactance element are produced. We have found that the input impedance, directivity and other characteristics of an antenna can'be improved over a wide frequency band because of the difference in frequencies between low frequency band and high frequency band used in television by suitably co'inbining said current components.

The present invention is based on the above described discovery and contemplates a multiconductor type broad band antenna characterized in that symmetrically disposed component sections of the antenna are short circuited by short circuiting elements at points other than their ends and that said component sections are respectively connected to feeder elements.

Accordingly it is the principal object of this invention to provide a novel antenna which can effectively operate over a broad frequency band.

Another object of this invention is to provide a novel television antenna of simple construction but can operate over a very `wide frequency band.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which we regard as our invention, it is believed that the invention will be better understood from the following description taken in connection with the accompanying drawing, in which FIG. 1 shows a diagram for explaining a multiconductor type circuit;

FIGS. 2(A), 3(A) and 4(A) show the component circuits of the circuit shown in FIG. l;

FIGS. 2(B), 3(B) and 4(B) show the respective cross sections of the circuit components shown in FIGS. 2(A), 3(A) and 4(A) and FIG. 5 represents a diagrammatic elevational view of an antenna embodying the principle lof this invention.

Referring now to the accompanying drawing FIG. l thereof shows a circuit comprising three parallel conductors 1, 2 and 3 with conductors 1 and 3 short circuited at an intermediate point. When it is assumed that a volt age is applied to one end, i.e. the lefthand end, of the conductor 2 and that the opposite ends of the conductors 1, 2 and 3 are short circuited as shown in FIG. 1, then it is able to consider that the circuit shown in FIG. 1 is constituted by three component circuits as shown in FIGS. 2(A) to 4(A). Impedances Zu, Zb and Zc of these component circuits are given respectively by where Zu, Zb and Zc represent -respectively the impedance of the component circuits, Ru resistance component, Xu reactance component, Wb the characteristic impedance of the component circuit shown in FIG. 3 (A), A wave length,

rice

W.3 the characteristic impedance of the component circuit shown in FIG. 4(A), L1 the distance between the lefthand end or the supply end of conductors 1, 2 and 3 and short circuiting point along conductors 1 and 3 and L2 represents the total length of the circuit.

In order to' fulfil these three critical transmission conditions the input impedance Zin should be represented by:

For the purpose of giving those skilled in the art, a better understanding of the invention, the derivation of Equation l is given below:

By representing the current distribution factor as a, and the voltage drop across and currents through the individual conductors in the transmission lines of FIG. l by V1, V2, V3, and Il, I2, I3, and, the supply voltages and currents through the individual conduct-ors in transmission lines of FIGS. 2(A) to 4(A) by Vu, Vb, Vc, and In, Ib, Ic, the relationship among these values can be represented by the formula:

V1 1 at 1-2a V..

V3 1 1-2a Vc (l-l) I1 (l 1 [u @H1-2. 0 1)(1.)

Is 1 l V2 Ic (1-2) and from these equations balanced and unbalanced voltages and currentscan be obtained as Since the second wire of the array of FIG. l is considered as being open-circuited at an intermediate part,

l1 :O and since the third wire is short-circuited,

Hence, impedances Zu, Zb and Zc of respective transmission line components can be given as and and

These values leads to the equation:

' 3 From this equation it follows:

From the above, the relation desired between voltage V2 and current I2 can be expressed by FIG. 5 shows our novel antenna having such an input impedance.

More particularly, where Zc approaches innity, the Equation 1 becomes:

Z. :(yyz pJA/YZ :QZ -1-Zb 1n u )2 b u On the other hand if the impedance Zh approaches to infinity, the Equation 1 becomes:

Referring now to FIG. 5 of the accompanying drawing there is shown an antenna according to this invention. The antenna comprises a pair of symmetrically disposed component sections 10 and 11 'each including three parallel conductors 10a, 10b and 10c and 11a, 11b and 11c which are interconnected by conductors 10d and 11d at their outer ends. A suitable source of high frequency energy 12 is connected across the inner terminals of the second conductors 10b and 11kJ of each section and the rst and third conductors 10a and 10c and 11 and 11c of each of said component sections are interconnected or short circuited by conductors 10e and 11e, respectively, at points intermediate the opposite ends of each section.

In order to provide the desired characteristics, in accordance with this invention the length L1, FIG. 5 or the distance between the short circuiting conductor 10 or 11e and the inner end of the component section is selected to be equal to 1A of the Wave length at a suitable frequency in a higher frequency band and the length L2 of each section to 1A of the wave length at a suitable frequency in a lower frequency band. By this design it is possible to provide an improved antenna which can satisfy the Equation 2 in a lower frequency band while the Equation 3 in a higher frequency band, thus operating effectively over a very wide band.

While the invention has been explained by describing particular embodiments thereof, it will be apparent that improvements and modications may be made without departing from the scop'e of the invention as delined in the appended claim.

What we claim as new and desire to secure by Letters Patent of the United States is:

A multiconductor type broad band antenna comprising a pair of symmetrically disposed component sections, each including three parallel conductors, -means to interconnect the outer ends of said conductors of each of said component sections, means to interconnect the inner ends of the first conductors of each of said component sections, means to feed an electric energy across inner ends of the second conductors of each of said component sections and means to short circuit the first and the third conductors of each of said component sections at a point intermediate the opposite 'ends thereof, the length of each of said component sections being selected to be equal to 1A of the wave length at a frequency in a lower frequency band and the length of the conductor between said short circuiting means and said feeding means of each of said component sections being selected to be equal to 1A of the wave length at a frequency in a higher frequency band.

References Cited by the Examiner UNITED STATES PATENTS 8/1963 Anderson 343-802 l/l965 Guertler 343-908 

